1. Field of the Invention
The present invention generally relates to a zoom lens control mechanism, as used in a camera and more particularly to a zoom lens control mechanism employing a non-linear adjustment relationship and a novel cam structure to effect rapid and accurate zooming and focusing.
2. The Related Art
In a camera with a zoom lens group, a conventional zoom lens control mechanism usually use a bolt-transmission structure to effect zooming. Such zoom lens control mechanism includes a guide device, a bolt and a transmission device. The bolt is extended along the optical axis of the zoom lens group, and has a knob which is fixed on the end of the bolt, thereby the bolt driven to cycle with rotating the knob. The transmission device is fixed on the zoom lens group and meshes with the bolt, thereby transferring circumrotation of the bolt to the zoom lens group so as to lead the zoom lens group moving along the guide device.
However, in zooming operation, due to the conventional zoom lens control mechanism converting circumrotation of the bolt to linear moving of the zoom lens group according to the linear ratio as the displacement to the rotated angle, the right focus length can not be acquired once rapidly in such a gradual adjustment mode. Further, the bolt with high precision is required but difficult to be manufactured. Moreover, the transmission device has to be added so that the whole structure design of the zoom lens control mechanism becomes complex with the manufacture cost increasing.
Thus, it is desired to provide a novel zoom lens control mechanism structure to improve the foregoing drawbacks.
An object of the present invention is to provide a zoom lens control mechanism structure in which a group of coupled faces like cam surfaces are utilized to convert the circumrotation to relative linear moving corresponding to the nonlinear relationship between relative linear displacement and rotated angle.
Another object of the present invention is to provide a zoom lens control mechanism with simplified structure and reduced manufacture cost.
To achieve the above objects, in accordance with the present invention, there is provided a zoom lens control mechanism including a lens barrel, a lens barrel support portion for the lens barrel seated on, a guiding device and a driving device. The lens barrel has three different diameter cylinders with the same center, and each of the cylinders has a post disposed at the bottom edge thereof and arranged with the imaginary center of the cylinders on the same line. Each of the cylinders except the innermost cylinder further has an elongated slot extended along the outer surface thereof. The guiding device is received in the two elongated slots and fixed on the outer surface of the innermost cylinder for leading the cylinders of the lens barrel moving relatively along the optical axis in the range of the allowable deviation. The lens barrel support portion includes three different diameter protruding cylinders which have the same center for mating with the corresponding cylinders of the lens barrel. Each of the protruding cylinders has plural projecting surfaces respectively for the corresponding post of the lens barrel seated on. The driving device is connected to the lens barrel support portion. In zooming operation, the driving device drives the lens barrel support portion rotating and consequently forcing the posts of the cylinders of the lens barrel to move respectively along the corresponding one of the projecting surfaces of the lens barrel support portion so as to effect zooming.